The present invention relates generally to the field of information processing by digital computers and, more particularly, to the entry and processing of information by application programs, particularly electronic spreadsheets.
Before computers, numerical analyses, particularly financial ones, were usually prepared on an accountant's columnar pad or spreadsheet, with pencil and calculator in hand. By organizing data into columns and rows, spreadsheets afford the rapid assimilation of information by a reader. The task of preparing a spreadsheet on paper, however, is not quite so fast. Instead, the process tends to be very slow, as each entry must be tediously calculated and entered into the spreadsheet. Since all calculations are the responsibility of the preparer, manually prepared spreadsheets are also prone to error. Hence, preparation of spreadsheets by hand is slow, tedious, and unreliable.
With the advent of microcomputers, a solution was forthcoming in the form of "electronic spreadsheets." Better known simply as "spreadsheets," these software programs provide a computerized replacement for the traditional financial modeling tools: the accountant's columnar pad, pencil, and calculator. In some regards, spreadsheet programs are to those tools what wordprocessors are to typewriters. Spreadsheets offer dramatic improvements in ease of creating, editing, and using financial models.
A typical spreadsheet program configures the memory of a computer to resemble the column/row or grid format of an accountant's columnar pad, thus providing a visual calculator for a user. Because this "pad" exists dynamically in the computer's memory, however, it differs from paper pads in several important ways. Locations in the electronic spreadsheet, for example, must be communicated to the computer in a format which it can understand. A common scheme for accomplishing this is to assign a number to each row in a spreadsheet, and a letter to each column. To reference a location at column A and row 1 (i.e., the upper-left hand corner), for example, the user types in "A1". In this manner, the spreadsheet defines an addressable storage location or "cell" at each intersection of a row with a column.
Data entry into an electronic spreadsheet occurs in much the same manner that information would be entered on an accountant's pad. After a screen cursor is positioned at a desired location, the user can enter alphanumeric information. Besides holding text and numeric information, however, spreadsheet cells can store special instructions or "formulas" specifying calculations to be performed on the data stored in spreadsheet cells. In this fashion, cell references can serve as variables in an equation, thereby allowing precise mathematical relationships to be defined between cells.
A particular advantage of electronic spreadsheets is the ability to create a multitude of "what if" scenarios from a single data model. This ability stems largely from the spreadsheet formulas, which are the means by which a user tells an electronic spreadsheet system how to manipulate and analyze one's data. After a set of mathematical relationships has been entered into a worksheet, the spread of information can be "recalculated" using different sets of assumptions, with the results of each recalculation appearing relatively quick. Performing this operation manually, with paper and pencil, would require recalculating every relationship in the model with each change made. Expectedly, electronic spreadsheets have quickly displaced their pencil-and-paper counterparts for modeling user information.
The structure and operation of a spreadsheet program, including spreadsheet formulas and "macros," are documented in the technical, trade, and patent literature. For an overview, see e.g., Cobb, D., Using 1-2-3, Que Corp., 1985; and Campbell, M., Quattro Pro 4.0 Handbook, 4th Ed., 1992. The disclosures of each of the foregoing references are hereby incorporated by reference.
Spreadsheet formulas are fundamental to the creation and operation of a spreadsheet data model. During creation of a particular spreadsheet or worksheet model, a user enters formulas in worksheet cells the same way he or she enters values and labels. Typically, a formula begins with a number or with a special character (e.g., +, -, (, @, ., #, or $) to distinguish the entry from raw data. More particularly, formulas are constructed from one or more of four basic components: operators, values, cell references, and @-functions. Each of these will be briefly reviewed.
Operators, which indicate how user data are to be combined and manipulated, typically include well-known operators such as -, +, *, /, and the like. Values are the information (e.g., numeric, logical, or text) which formulas are to act upon. To include a value in a formula, the user simply types it as he or she desires it to appear.
Cell references, on the other hand, allow a user to employ a value in one's current formula that is derived from another cell. For instance, if a cell having an address of B3 contains the value of 10, the formula 5+B3 placed in any other cell of the spreadsheet will evaluate to the result of 15. A referenced cell containing no value (blank) or a label is, depending on implementation, treated as zero or as an error (ERR). Much of the flexibility of electronic spreadsheets stems from this ability to establish relationships via cell references.
Spreadsheet functions or "@-functions" are built-in formulas provided for frequently-used calculations. Some @-functions perform a calculation on a single value, such as @SQRT(n) which calculates the square root of the number n. Other @-functions perform calculations on cell ranges, such as @SUM(B3 . . . B10) which sums the values stored in cells B3 to B10. @-Functions can be used in formulas where one might use a value or cell reference.
As application programs such as spreadsheets have become more developed, many new functions that users may perform on the data have been added. These functions have been added to satisfy the user's need to perform various mathematical, statistical, and financial computations. Each function has a unique name or identifier to invoke the function. Each function often requires a particular number of parameters on which to operate. However, the addition of these new functions has increased the number of functions into the hundreds for a typical spreadsheet. Thus, it has become difficult for users to remember all the different functions, as well as the parameters for each function. Hierarchial nesting of function invocations also adds complexity for the user.
One problem with many programs in the prior art is accurately entering or editing the data for use by the program. This is especially a concern when entering or editing formulas involving a function invocation in a spreadsheet. It is often difficult for the user to keep track of the portion of the formula that is being presently input or edited. The inability to identify the formula components often causes users to introduce errors into a particular cell formula, thus affecting the accuracy of the entire spreadsheet.
While there have been attempts in the prior art to eliminate these problems, existing spreadsheets are only moderately successful in increasing user access to help and other functions. Many spreadsheets presently offer on-line help, however, the information provided is only nominally helpful, and the process of getting to the help information is very difficult. With most on-line systems, the information is often limited to a single line of information and provides the user with only nominal assistance.
With the present trend of employing electronic spreadsheets to model increasingly complex data models, the ability of most users to correctly enter complex formulas using present-day electronic spreadsheet systems has become taxed. Accordingly, there is much interest in improving the process of inputting and editing cell formulas in electronic spreadsheet systems.